In recent years, sound combination technologies of converting text information into sounds, sound recognition technologies of recognizing content uttered by users as text information, and natural language processing technologies of recognizing content indicated by sentences have been developed. Therefore, by applying these technologies, user interfaces (UIs) for enabling various household electrical appliances such as television receivers, information devices such as personal computers, and in-vehicle devices such as car navigation systems to be manipulated by allowing users to input various instructions as natural sentences have become more common. For example, Patent Literature 1 discloses an example of a user interface for enabling various devices to be manipulated by allowing a user to input various instructions as natural sentences.
In addition, in recent years, information devices such as so-called smartphones or tablet terminals capable of adding new functions by installing applications have also become more common. With the multiple functions of such devices, manipulations of selecting the functions are complicated when users execute desired functions. Therefore, convenience of interfaces for executing desired functions in various devices by allowing users to input various instructions as natural sentences has been improved.